1. Field of the Invention
This invention relates to a method of restricting the flow of flowable radiation curable material by forming a dam of the material.
2. Background Information
In the art of making bosses, restriction of a liquid plastic was accomplished by pouring it onto the surface to form a protrusion which remained due to surface tension. Improvement to get better relief and definition was accomplished by flowing the liquid plastic to a sharp peripheral edge or it was poured into a cavity. To achieve this sharp peripheral edge, a retaining edge or dam was screened onto the face of a plastic sheet. The dam then acted as a retaining wall to hold the liquid plastic. The screen processes are complex and the results were not as good as desired. In U.S. Pat. No. 4,353,858, issued Oct. 12, 1982, Gilleo et al described a method of making a dam to retain a liquid plastic. The dam is formed by using a debossing die and impressing it into a heated thermoplastic substrate to form the dam. Gilleo et al in U.S. Pat. No. 4,409,264, issued Oct. 11, 1983, teach another method of retaining liquid plastic by forming a pattern on a surface. The pattern is formed by a contiguous low energy surface having a surface energy of between about 5 and about 20 dynes/cm, as the retaining means. Liquid resin is introduced to the pattern area in a quantity sufficient to form a liquid resin surface elevated above the article surface and in a quantity insufficient to flow past the retaining means due to the force of gravity.
Whereas the above methods may be useful for forming bosses made from plastics, the present invention relates to the use of flowable radiation curable material on substrates which can be hard or flexible materials, including thermoset materials, glass, metal, ceramic, and the like. The substrate can be planar, with or without being populated with devices such as electronic devices. The substrate is to be coated with the flowable radiation curable material in certain defined areas. The problem faced was how to coat only defined areas with flowable radiation curable material in an efficient manner.